The HELLAS2XMM survey.: VII.: The hard X-ray luminosity function of AGNs up to z=4:: More absorbed AGNs at low luminosities and high redshifts

被引:353
作者
La Franca, F
Fiore, F
Comastri, A
Perola, GC
Sacchi, N
Brusa, M
Cocchia, F
Feruglio, C
Matt, G
Vignali, C
Carangelo, N
Ciliegi, P
Lamastra, A
Maiolino, R
Mignoli, M
Molendi, S
Puccetti, S
机构
[1] Univ Roma Tre, Dipartimento Fis, I-00146 Rome, Italy
[2] Osserv Astron Roma, INAF, I-00100 Monte Porzio Catone, Italy
[3] Osservatorio Astron Bologna, INAF, I-40127 Bologna, Italy
[4] Max Planck Inst Extraterr Phys, MPE, D-85741 Garching, Germany
[5] Univ Bologna, Dipartimento Astron, I-40127 Bologna, Italy
[6] Univ Milan, I-20126 Milan, Italy
[7] Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy
[8] IASF, INAF, I-20133 Milan, Italy
关键词
diffuse radiation; galaxies : active; galaxies : evolution; quasars : general; surveys; X-rays : diffuse background;
D O I
10.1086/497586
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We have determined the cosmological evolution of the density of active galactic nuclei (AGNs) and of their N-H distribution as a function of the unabsorbed 2 - 10 keV luminosity up to redshift 4. We used the HELLAS2XMM sample combined with other published catalogs, yielding a total of 508 AGNs. Our best fit is obtained with a luminosity-dependent density evolution (LDDE) model where low-luminosity (L-X similar to 10(43) ergs s(-1)) AGNs peak at z similar to 0.7, while high-luminosity AGNs (L-X > 10(45) ergs s(-1)) peak at z similar to 2.0. A pure luminosity evolution model (PLE) can instead be rejected. There is evidence that the fraction of absorbed (N-H > 10(22) cm(-2)) AGNs decreases with the intrinsic X-ray luminosity and increases with the redshift. Our best-fit solution provides a good fit to the observed counts, the cosmic X-ray background, and to the observed fraction of absorbed AGNs as a function of the flux in the 10(-15) ergs cm(-2) s(-1) < S2-10 < 10(-10) ergs cm(-2) s(-1) range. We find that the absorbed, high-luminosity (L-X > 10(44) ergs s(-1)) AGNs have a density of 267 deg(-2) at fluxes S2-10 > 10(-15) ergs cm(-2) s(-1). Using these results, we estimate a density of supermassive black holes in the local universe of rho(BH) = 3.2 h(70)(2) x 10(5) M-circle dot Mpc(-3), which is consistent with the recent measurements of the black hole mass function in the local galaxies.
引用
收藏
页码:864 / 879
页数:16
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